JPS62119560A - Electrophotographic device for reversal development system - Google Patents

Abstract

PURPOSE:To prevent the degradation of a photosensitive body due to the partial rise of charged potential by providing a means which controls an electrostatic charger in accordance with the displacing speed of the photosensitive body. CONSTITUTION:A microprocessor 20 gives a driving command of a motor 14 to a motor control circuit 24. The motor 14, namely, a photosensitive drum 12 starts to rotate in accordance with this command, and the microprocessor 20 sets a timer. Thereafter, the microprocessor 20 judges whether the motor 14 is rotated uniformly or not by the presence/absence of a lock signal from the motor control circuit 24. If the lock signal is present, the microprocessor 20 gives a certain voltage to a charging corotron 16, and electrostatic of the photosensitive drum 12 is started at this time, and the developing bias of a developing device 18 is turned on after a certain time to enter the next process. Thus, the unevenness of electrostatic charge in the initial stage of rotation is eliminated to prevent effectively the degradation of the photosensitive drum 12.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electrophotographic apparatus using a reversal development method, and more particularly to an electrophotographic apparatus such as an electronic copying machine or a printer.

(Prior art) For example, the Journal of the Institute of Electronics and Communication Engineers Vol. J61-CNo.
7 (197B) on pages 416 to 423,
An electrophotographic apparatus using a reversal development method is disclosed. In such a reversal development method, when the photoreceptor drum is rotated without being charged, since the photoreceptor is an insulator, the surface of the photoreceptor drum is induced to be negatively polarized by the positively charged toner, and the surface of the photoreceptor drum is electrostatically polarized. Toner adheres to the surface of the photoreceptor drum. Continuing this state for a long time is a waste of toner, so in an electrophotographic apparatus using a reversal development system, charging is generally performed at the same time as the photoreceptor drum starts rotating.

(Problems to be Solved by the Invention) However, if the photosensitive drum is charged while the rotational speed is not sufficient, the amount of charge per unit area will be larger in the portion where the rotational speed is slow than in the subsequent portion. As a result, there is a problem in that the charged charge becomes non-uniform, and deterioration of the photoreceptor drum is accelerated in portions that are charged more than a predetermined level, so that the life of the photoreceptor drum as a whole is not very long.

Therefore, a main object of the present invention is to provide an electrophotographic apparatus of a reversal development type that can prevent deterioration of a photoreceptor due to a partially high charging potential.

(Means for Solving the Problems) To put it simply, the present invention includes a photoconductor on which an electrostatic latent image is sequentially formed according to the displacement of the photoconductor, a charger for uniformly charging the photoconductor, and a photoconductor. This is an electrophotographic apparatus of a reversal development type, which is equipped with means for controlling a charger according to the displacement speed of the body.

(Function) When the displacement speed of the photoreceptor becomes sufficiently large, the photoreceptor begins to be uniformly charged by the charger.

(Effects of the Invention) According to the present invention, it is possible to prevent the charger from charging the photoreceptor while the displacement speed of the photoreceptor is slow, so that the photoreceptor deteriorates due to being charged more than a predetermined amount of charge in that part. can be suppressed as much as possible.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

(Embodiment) FIG. 1 is a block diagram of essential parts showing an embodiment of the present invention. The photosensitive drum 12 is rotationally driven by a motor 14 . Charging corotrons 1 are placed in the vicinity of the photoreceptor drum 12 sequentially in the rotational direction of the photoreceptor drum 12.
6 and a developing device 18 are arranged. This charging corotron 16 and developing device 18 are controlled by a microprocessor 20. That is, the microprocessor 20 controls a voltage unit (not shown) so as to apply a necessary voltage to the charging corotron 16 and a developing bias to the developing device 18.

A rotary encoder 22 is connected to the motor 14 for driving the photosensitive drum 12, and an electric signal corresponding to the rotation of the motor 14 is supplied from the rotary encoder 22 to a motor control circuit 24.

This motor control circuit 24 includes, for example, an integrated circuit "TC9142P" manufactured by Toshiba. The motor control circuit 24 includes a phase-locked loop that receives a rotation signal from the rotary encoder 22. A lock signal from the phase-locked loop is applied to the microprocessor 20, and the pulse or voltage controlled by the phase-locked loop is , applied to the drive motor 14.

Note that a command signal for driving or stopping the motor 14 is given to the motor control circuit 24 from the microprocessor 20.

Next, referring to FIG. 2, the operation of the embodiment shown in FIG. 1 will be explained. The microprocessor 20 first gives a drive command for the motor 14 to the motor control circuit 24 . depending on,
A motor drive signal is applied from the motor control circuit 24, and the motor 14, that is, the photosensitive drum 12 starts rotating. Subsequently, the microprocessor 20 clocks a timer (not shown) attached to the microprocessor 20.

Thereafter, the microprocessor 20 controls the motor control circuit 24
It is determined whether the motor 14 is in a constant rotation state based on the presence or absence of a lock signal from the motor. If there is a lock signal from the motor control circuit 24, the microprocessor 20 applies a constant voltage to the charging corotron 16 in response to the lock signal, so that the photoreceptor drum 12 starts being charged from that point on. After a certain period of time has elapsed, the microprocessor 20 turns on the developing bias of the developing device 18 and proceeds to the next process.

If a lock signal is not obtained from motor control circuit 24, microprocessor 20 then determines whether the previously set timer has elapsed.

If the motor does not lock and a time-up occurs, the microprocessor 20 treats it as a motor error,
Terminate the process.

Thus, according to this embodiment, the microprocessor 2
0 means that the charged corotron 1 is activated immediately after the motor 14 is locked.
Turn on 6. In other words, in this embodiment, the charging corotron 16 is not turned on unless the rotational speed of the motor 14 reaches a certain level. Therefore, there is no uneven charging at the initial stage of rotation, and deterioration of the photosensitive drum 12 is effectively prevented.

Note that in the above-mentioned embodiments, a drum was used as the photoreceptor. However, the present invention can be applied to all types of electrophotographic devices in which the surface of a photoreceptor is charged or an electrostatic latent image is formed while being displaced.

Further, in the above embodiment, a phase locked loop was used to detect whether the displacement of the photoreceptor exceeded a predetermined value. However, it goes without saying that a speed detector may also be used. In this case, when the speed detector detects that the rotation of the motor 14, that is, the displacement of the photoreceptor exceeds a certain speed, the microprocessor 20 will turn on the charging corotron.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing one embodiment of the present invention. FIG. 2 is a flow diagram for explaining the operation of the embodiment shown in FIG. In the figure, 12 is a photosensitive drum, 14 is a motor, and 16
20 is a charging corotron, 20 is a microprocessor, 22 is a rotary encoder, and 24 is a motor control circuit. Patent applicant Sanyo Electric Co., Ltd. agent Patent attorney Yama 1) Yoshito (and 1 other person) Figure 1 Figure 2-1

Claims (1)

[Scope of Claims] 1. A photoconductor on which an electrostatic latent image is sequentially formed in accordance with the displacement thereof, a charger for uniformly charging the photoconductor, and a charger that charges the photoconductor in accordance with the displacement speed of the photoconductor. An electrophotographic device using a reversal development method and equipped with means for controlling the device. 2. The device according to claim 1, comprising means for determining whether the speed of the photoreceptor has reached a predetermined value or higher, and means for causing the charger to perform charging according to the output of the determining means. An electrophotographic device that uses reversal development.